The Short-Term and Intermediate-Term Risk of Second Neoplasms After Diagnosis and Treatment of Unilateral Vestibular Schwannoma: Analysis of 9460 Cases

Purpose: To determine the incidence of second intracranial neoplasms after the diagnosis and treatment of sporadic vestibular schwannoma (VS).

Methods and materials: Analysis of the Surveillance, Epidemiology, and End Results (SEER) database including all patients identified with a diagnosis of VS and a second intracranial tumor. The Kaplan-Meier method was used to determine the incidence of second tumors while allowing for censoring at loss to follow-up or death. Multivariable associations between treatment modality and second tumor formation were explored using Cox proportional hazards regression analysis. Two illustrative cases are also presented.

Results: In all, 9460 patients with unilateral VS were identified between 2004 and 2012. Overall, 66 (0.7%) patients experienced a separate intracranial tumor, benign or malignant, after treatment of VS. Kaplan-Meier estimates for time to second neoplasm at 1, 3, and 5 years were 0.3%, 0.7%, and 0.8%, respectively. Multivariable comparison between VS treatment modalities revealed that the risk of second tumor formation was similar between radiation and surgery (hazard ratio [HR] 0.74; 95% confidence interval [CI] 0.36-1.51; P=.93) but greater for tumors managed with observation alone compared with radiation (HR 2.48; 95% CI 1.31-4.71; P<.01). A total of 6 (0.06%) intracranial malignancies were diagnosed after VS treatment. Kaplan-Meier estimates for time to malignancy at 1, 3, and 5 years were 0%, 0.1%, and 0.1%, respectively. After adjustment for age at diagnosis, sex, and treatment modality, the probability of malignancy after radiation was not greater than after observation alone or microsurgery (HR 4.88; 95% CI 0.85-28.14; P=.08) during the study period.

Conclusions: The risk for the development of a second intracranial neoplasm, benign or malignant, at 5 years after treatment of unilateral VS is approximately 0.8%, whereas the risk of acquiring a separate malignancy is 0.1%, or approximately 1 per 1000 cases. The short-term and intermediate-term incidence of second neoplasm after radiation of VS is not greater than the incidence after microsurgery or observation.